A single-shot diagnostic platform based on copper nanoclusters coated with cetyl trimethylammonium bromide for determination of carbamazepine in exhaled breath condensate.

A fluorescent nanoprobe is designed for the determination of carbamazepine (CBZ) in exhaled breath condensate (EBC) of patients receiving CBZ. The probe consists of copper nanoclusters (Cu NCs) coated with cetyl trimethylammonium bromide. The interaction of probe with CBZ results in blocking non-radiative e-/h+ recombination defect sites on the surface of Cu NCs and consequently enhancing the blue-green fluorescence of Cu NCs (excitation/emission wavelengths: 290/480 nm). The experimental conditions were optimized using a response surface methodology (central composite design). Under the optimized conditions, the calibration plot is linear in the 0.2 to 20 µg mL-1 CBZ concentration range and the detection limit is as low as 0.08 µg mL-1. The intra-day and inter-day relative standard deviations for six replicated measurements of 10 µg mL-1 CBZ are 3.9% and 4.8%, respectively. The method was applied for the determination of CBZ level in EBC of patients receiving CBZ. The accuracy of the method was confirmed by HPLC-UV analysis as a reference method. Graphical abstract Graphical abstract contains poor quality and small text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf. "Figures 1 contains poor quality of text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.A new PDF format of Graphical Abstract was provided in attachment section. Schematic presentation of cetyl trimethylammonium bromide coated copper nanocluster's response to carbamazepine.

Electropolymerization of taurine on gold surface and its sensory application for determination of captopril in undiluted human serum.

Polytaurine film was electrodeposited on gold (Au) electrode through cyclic voltammetry from taurine and phosphate buffer solution. The electrocatalytic effect of polytaurine modified Au (PT/Au) electrode was investigated for electro-oxidation of captopril (CAP). Electrocatalytical activity of PT/Au electrode was studied using cyclic voltammetry (CV), chronoamperometry and differential pulse voltammetry (DPV). DPV was used to evaluate the analytical performance of CAP in the presence of phosphate buffer solution and good limit of detection was obtained by this sensor. The experimental conditions influencing the determination of CAP were optimized and under optimal conditions, the oxidation peak current was proportional to CAP concentration in the range of 0.06-0.2 µM, while the detection limit was 0.03 µM (S/N=3). The results revealed that PT promotes the rate of oxidation by increasing the peak current. Finally, the applicability of the method to direct assay of human serum is described. The proposed sensor was successfully applied to determine cadaverine in fish samples, yielding satisfactory results. The spiked recoveries were in the range of 96.0-105.0%.

Simultaneous determination of codeine and caffeine using single-walled carbon nanotubes modified carbon-ceramic electrode.

In the present paper, the simultaneous determination of codeine (CO) and caffeine (CF) is described by the use of single-walled carbon nanotubes modified carbon-ceramic electrode (SWCNT/CCE); prepared via a simple and rapid method. The results show that the SWCNT/CCE exhibits excellent electrochemical catalytic activity toward the oxidation of these compounds with respect to the bare CCE and offers two anodic peaks at 1.05 and 1.38 V vs. saturated calomel electrode for oxidation of CO and CF, respectively. Differential pulse voltammetry was used for simultaneous determination of CO and CF at micromolar concentration level. In the optimum conditions, it is found that the calibration graphs for CO and CF are linear in the concentration ranges 0.2-230 and 0.4-300 µM with detection limits of 0.11 and 0.25 µM for CO and CF, respectively. The SWCNT/CCE presents good stability, reproducibility, and repeatability and the proposed method has been successfully applied for determination of CO and CF in some pharmaceutical, drinking and biological samples with high recovery rate.

Detection and discrimination of recombinant plasmid encoding hepatitis C virus core/E1 gene based on PNA and double-stranded DNA hybridization.

Development of an electrochemical DNA biosensor for direct detection and discrimination of double-stranded plasmid (ds-Pl) without the need for denaturation of the target plasmid sample using a peptide nucleic acid (PNA) oligomer as the probe is described. This goal was achieved by modification of gold electrode with 6-mercapto-1-hexanol following monolayer self-assembly of cysteine conjugated 20-mer PNA oligomer probe, complementary to the HCV core/E1 region, which binds to ds-Pl and forms PNA/ds-Pl structure. The significant variation in differential pulse voltammetric response of methylene blue on the probe modified electrode upon contacting with complementary double-strand plasmid to form PNA/ds-Pl triplex structure is the principle of target plasmid detection. The results indicated that the reduction peak current was linear with the concentration of complementary strand in the range of 10-300 pg/µl with a detection limit of 9.5 pg/µl.

Differential pulse voltammetric simultaneous determination of acetaminophen and ascorbic acid using single-walled carbon nanotube-modified carbon-ceramic electrode.

Single-walled carbon nanotube-modified carbon-ceramic electrode (SWCNT/CCE) was employed for the simultaneous determination of acetaminophen (APAP) and ascorbic acid (AA). The SWCNT/CCE displayed excellent electrochemical catalytic activities toward APAP and AA oxidation compared with bare CCE. In the differential pulse voltammetry technique, both AA and APAP gave sensitive oxidation peaks at -62 and 302 mV versus saturated calomel electrode, respectively. Under the optimized experimental conditions, APAP and AA gave linear responses over ranges of 0.2 to 150.0 µM (R(2)=0.998) and 5.0 to 700.0 µM (R(2)=0.992), respectively. The lower detection limits were found to be 0.12 µM for APAP and 3.0 µM for AA. The investigated method showed good stability, reproducibility, and repeatability as well as high recovery in pharmaceutical and biological samples.

Introduction of hematoxylin as an electroactive label for DNA biosensors and its employment in detection of target DNA sequence and single-base mismatch in human papilloma virus corresponding to oligonucleotide.

For the detection of DNA hybridization, a new electrochemical biosensor was developed on the basis of the interaction of hematoxylin with 20-mer deoxyoligonucleotides (from human papilloma virus, HPV). The study was performed based on the interaction of hematoxylin with an alkanethiol DNA probe self-assembled gold electrode (ss-DNA/AuE) and its hybridization form (ds-DNA/AuE). The optimum conditions were found for the immobilization of HPV probe on the gold electrode (AuE) surface and its hybridization with the target DNA. Electrochemical detection of the self-assembled DNA and the hybridization process were performed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) over the potential range where the accumulated hematoxylin at the modified electrode was electroactive. Observing a remarkable difference between the voltammetric signals of the hematoxylin obtained from different hybridization samples (non-complementary, mismatch and complementary DNAs), we confirmed the potential of the developed biosensor in detecting and discriminating the target complementary DNA from non-complementary and mismatch oligonucleotides. Under optimum conditions, the electrochemical signal had a linear relationship with the concentration of the target DNA ranging from 12.5 nM to 350.0 nM, and the detection limit was 3.8 nM.

Direct and rapid electrochemical biosensing of the human interleukin-2 DNA in unpurified polymerase chain reaction (PCR)-amplified real samples.

Electrochemical detection of polymerase chain reaction (PCR)-amplified human interleukin-2 (IL-2) coding DNA sample (399bp size) without any purification and pre-treatment is described. To achieve this goal, a sensor was made by immobilization of a 20-mer oligonucleotide (chIL-2) as the probe on the pencil graphite electrode (PGE). This probe is related to the antisense strand of human interleukin-2 gene. The results showed that the electrode could effectively sense the PCR product of human interleukin-2 DNA by anodic differential pulse voltammetry (ADPV) based on guanine oxidation signal. In order to inhibit PCR components interfering effects and improve biosensing performance, various factors were investigated. We found that the desorption of non-specifically adsorbed components of the unpurified PCR samples from PGE surface is easily achieved by washing of the electrode in washing solution for about 300s. The effectiveness of this procedure was confirmed using purified PCR samples. The selectivity of the sensor was assessed with negative control PCR sample and seven different non-complementary PCR products corresponding to 16S rDNA (bigger than 1500bp) of various bacterial genuses. Diagnostic performance of the biosensor is described and the detection limit is found to be 69pM. The reliability of the electrochemical biosensing results was verified by electrophoresis of the PCR products.

Construction, electrochemically biosensing and discrimination of recombinant plasmid (pEThIL-2) on the basis of interleukine-2 DNA insert.

Construction, electrochemically biosensing and discrimination of recombinant pEThIL-2 plasmid, with 5839bp size, on the basis of interleukine-2 (IL-2) DNA insert are described. Plasmid pEThIL-2 was constructed by PCR amplification of IL-2 encoding DNA and subcloning into pET21a(+) vector using BamHI and SacI sites. The recombinant pEThIL-2 plasmid was detected with a label-free DNA hybridization biosensor using a non-inosine substituted probe. The proposed sensor was made up by immobilization of a 20-mer antisense single strand oligonucleotide (chIL-2) related to the human interleukine-2 gene on the pencil graphite electrode (PGE) as a probe and then the sensing of recombinant pEThIL-2 plasmid was conducted by anodic differential pulse voltammetry (ADPV) based on guanine oxidation signal. Selectivity of the detection was assessed with pET21a(+) non-complementary plasmid, with 5443bp size, lacking IL-2 encoding DNA. Different factors such as electrode activation conditions and washing strategy were tested in order to eliminate the nonspecific adsorption of pET21a(+). We have found that the PGE activation for 300s produces a condition in which desorption of nonspecifically adsorbed plasmids from the electrode surface can be achieved by 300s washing of the electrode in 20mM Tris-HCl buffer solution (pH 7.0) containing 20mM NaCl. Diagnostic performance of the biosensor is described and the detection limit is found to be 10.31pg/microL.